Polarized electromagnet



ug- 5, 1969 e. DI MARCO 3,460,079

' POLARIZED ELECTROMAGNET Filed July '7. 196? 2 Sheets-Sheet l All@ 51969 B. DI MARCO 3,460,079

POLARI ZED ELECTROMAGNET Filed July 7. 196'? 2 Sheets-Sheet 2 4/ -/d, lfI z l r 31 ,C ...E I a- .5. M4# 1 l l if? Jr A l# L JA L 4Z im Q 55.5.4//f /5/ Mik-i Wu fm W@ @M5/Q A M United States Patent O 3,460,079POLARIZED ELECTROMAGNET Bernard Di Marco, Lincoln Park, Mich., assignorto I-T-E Imperial Corporation, Philadelphia, Pa., a corporation ofDelaware Filed July 7, 1967, Ser. No. 651,912 Int. Cl. H01f 7/08 U.S.Cl. 335-230 8 Claims ABSTRACT OF THE DISCLOSURE An electromagnet unitbiased to open position is maintained in closed position by a permanentmagnet that is part of the yoke assembly. The latter is generallyE-shaped and consists of a first generally U-shaped stack of laminationproviding the outer legs of the E, and a second generally I-shaped stackof lamination providing the center leg of the E. E-shaped non-magneticstainless steel retainers maintain the lamination stacks in operativepositions, with these operative positions being such that the stacks andretainers cooperate to form a pocket wherein a slablike ceramicpermanent magnet is retained. The armature is constructed of a Hat sheetof steel.

This invention relates to electromagnets in general and in particularrelates to a novel construction of an electromagnet that can beenergized and deenergized by the application of instantaneous voltagesignals and will remain in the position dictated by the last appliedsignal even if all power is removed from the operating coil.

Copending application Ser. No. 568,249 filed July 27, 1966, entitledIndustrial Control Relay with B. Di Marco et al. as inventors andassigned to the assignee of the instant invention, discloses anelectromagnetic contactor of a type often referred to as an industrialcontrol relay. Briey, an electromagnetic contactor is a multi-poleswitch having biasing means urging the switch arms to a iirst positionand an electromagnet which when energized acts against the biasing meansto operate the switch arms to a second position. For the most part,prior art electromagnetic contactors are so constructed that theoperating coil must be continuously energized to maintain the switchmeans in the second position.

This often leads to undesirable conditions. In particular, by momentaryloss of control power, the magnet coil will be deenergized and theswitch means will not be maintained in its second position. Further,continuous currents flow through the magnet operating coil requiringexcessively large winding size to prevent overheating.

In order to overcome these disadvantages, for some applications theprior art has provided mechanical latches and permanent magnet latchesto maintain the switch arms in the second position against the force ofbiasing means urging the switch arms to the first position. The instantinvention is concerned with the permanent magnet type latch forelectromagnetic contactors.

In particular, the device of the instant invention includes a novelconstruction for an E-shaped magnet yoke assembly including a permanentmagnet. High strength permanent magnets of convenient shapes are readilyconstructed of ceramic material. In the case of a magnet of sheet-likeor slab-like shape, the magnetization axis may be perpendicular to theplane of the slab as in the device of the instant invention. TheE-shaped yoke assembly provides a pocket for the slab without lshortingthe magnet by utilizing non-magnetic retainer plates constructed ofstainless steel to maintain two stacks of lamination in operativepositions. The rst stack is generally U-shaped and provides therelatively narrow outer legs of the E while 3,460,079 Patented Aug. 5,1969 the second stack is generally I-shaped and provides the relativelywide center leg ofthe E about which the electromagnet operating coil iswound. The armature is simply a flat sheet of steel secured to means forconnecting the armature to a movable contact carrier.

Accordingly, a primary object of the instant invention is to provide anovel construction for an electromagnet device having a permanent magnetlatch.

Another object is to provide an electromagnet of this type having anovel yoke assembly construction including a ceramic permanent magnet.

Still another object is to provide an electromagnet of this type inwhich the yoke assembly includes two stacks of lamination maintained inoperative positions by nonmagnetic sheet-like members with the stacksand sheetlike members cooperating to form a pocket wherein a plate-likepermanent magnet is disposed.

These objects as well as other objects of the instant invention willbecome readily apparent after reading the following description of theaccompanying drawings in which:

FIGURE 1 is an exploded perspective showing the main assemblies of anelectromagnet constructed in accordance with the teachings of theinstant invention.

FIGURE 2 is an exploded perspective of the yoke assembly of FIGURE l.

FIGURE 3 is a side elevation of the yoke assembly.

FIGURE 3A is an end view of the yoke assembly looking in the directionof arrows 3A--3A of FIGURE 3.

FIGURE 4 is a side elevation of one of the non-magnetic retainer platesof the yoke assembly.

FIGURE 4A is a cross-section taken through lines 4A- 4A of FIGURE 4looking in the direction of arrows 4A- 4A.

FIGURE 5 is a plan view of the armature assembly.

FIGURE 5A is a side elevation of the armature assembly looking in thedirection of arrows SA-SA of FIG- URE 5.

FIGURE 6 is an electrical schematic illustrating a control circuitincluding the electromagnet of FIGURE l.

As best seen in FIGURE 1 electromagnet 10, constructed in accordancewith the teachings of the instant invention, includes E-shaped yokeassembly 11, coil assembly 12 having aperture 12a to receive the centerleg of yoke assembly 11, and armature assembly 13. With particularreference to FIGURE 2, itis seen that yoke assembly 11 consists ofgenerally U-shaped lamination stack 14, generally I-shaped laminationstack 15, rectangular plate-like ceramic permanent magnet 16, E-shapednonmagnetic stainless steel retainer plates 17, 17 and six rivets 18 forretaining elements numbered 14-17 together as a unitary structure.

Lamination stack 14 provides the relatively narrow outer legs 14a, 14band base 14c of a generally E-shaped magnet yoke while lamination stack15 provides the relatively wide center leg 15a of the magnet yoke. Thelower ends of lamination stack 15 is provided with lateral projections15b, 15C which, as best seen in FIGURE 3, extend beyond the shorteredges of permanent magnet 16 to act as a flux collector. However,projections 15b, 15e terminate a considerable distance from outer legs14a, 14b so as not to short-circuit the flux generated by permanentmagnet 16.

Permanent magnet 16 is slightly wider than lamination stacks 14, 15 inorder to provide suflicient permanent magnet flux for magneticallylatching electromagnet 10 against the force of return spring 34 (FIGURE6). Thus, each retainer plate 17 is provided with a shallow generallyrectangular recess 19 (FIGURE 4A) to receive the longer edges ofpermanent magnet 16. Shallow recess 20 (FIG- URE 3) wherein permanentmagnet 16 is disposed is 3 formed through the cooperation of laminationstacks 14, 15.

As seen in FIGURE 5 armature assembly 13 consists of magnetic platearmature 40 with connecting member 41 welded or otherwise secured to theupper surface of armature 40. Central portion 41a of member 41 is formedaway from the upper surface of armature 40 to provide a shallow passage42 extending the full width of armature 40 at the center thereof. In amanner well-known to the art, aperture 42 is adapted to receive means(not shown) for mechanically connecting armature assembly 13 to themovable contacts of a contactor for operation thereof.

As seen in the schematic of FIGURE 6, coil assembly 12 includes ON coil21, OFF coil 22 and semiconductor diode 25 paralleled by surgeprotective device 24. Coils 21, 22 are multiturned windings each havingan end thereof connected to one electrode of diode 25 by conductor 26internally of coil assembly 12. The other electrode of diode 25 isconnected to terminal 30 extending externally of coil assembly 12 forconnection to one terminal L-1 of an AC control power source (notshown). The other ends of coils 21, 22 are connected to insulationcovered conductors 21a, 22a, respectively, which extend externally ofcoil assembly 12. Elements 21, 22, 24 and 25 are encapsulated in asuitable plastic material forming body 23 thereby providing coilassembly 12 as a unit which is highly resistant to mechanical shock andother harmful environmental conditions including high humidity.

Switches 28, 29 (FIGURE 6) are normally closed and normally opened,respectively. Switch 28 is interposed between lead 21a and one of thestationary contacts of ON control switch 31 Whose other stationarycontact is connected to the other terminal L-2 of the AC control voltagesource. Switch 29 is interposed between lead 2lb and one of thestationary contacts of OFF control switch 32 whose other stationarycontact is connected to terminal L-2.

Operation of electromagnet proceeds as follows. Starting with armatureassembly 13 in its released position remote from yoke assembly 11,having been moved there by return spring 34 (FIGURE 6), ON control 31 isclosed to complete an energizing circuit for ON coil 21, such circuitextending from terminal L-l, through diode 25 acting as a halfwaverectifier, ON coil 21, switch 28 and control 31 to terminal L-Z. Withthis energizing circuit completed current flows through ON coil 21 in adirection generating flux which aids the liux generated by permanentmagnet 16 and is of sufficient magnitude to operate armature assembly 13against the force of return spring 34 toward yoke 11 to latchedposition. In moving to its latched position, armature assembly 13 opensswitch 28, closes switch 29, and also operates additional switch unitsof the contactor (not shown).

When ON coil 21 is deenergized by opening ON control 31, armatureassembly 13 remains in latched position in that the flux of permanentmagnet 16 is of sufficient strength to maintain armature 40` inengagement with lamination stacks 14, 15. Closing of OFF` control 32 atthis time completes an energizing circuit for OFF coil 22, such circuitbeing from terminal L-1, through halfwave rectifier diode 25, OFF coil22, the now closed switch 29, OFF control switch 32 to terminal lf2.Current flowing in OFF coil 22 generates liux in the magnetic framecomprising armature 40 and lamination stacks 14, 15, opposing the fiuxof permanent magnet 16 with the net flux being of insufficient strengthto maintain armature assembly 13 latched against the force of returnspring 34. Thus, return spring 34 operates armature assembly 13 to itsreleased position shown in FIGURE 6 and in so doing opens switch 29 andcloses switch 28 so that upon subsequent operation of ON control 31 theenergizing circuit for ON coil 21 may be completed.

It is noted that in FIGURE 6 the arrows for the respective coils are notto indicate current flow but rather to indicate that the fluxesgenerated by coils 21, 22 are in opposite directions through magneticframe 14, 15, 40 when the respective coil energizing circuits arecompleted,

Thus, it is seen that the instant invention provides a novelconstruction for an electromagnet having a permanent magnet latch. Inparticular, the permanent magnet is a plate-like ceramic member in aplane perpendicular to and at the base end of the center leg of anE-shaped yoke. The magnetic frame and the permanent magnet elements ofthe yoke assembly are positioned and maintained as a unitary structureby stainless steel side plates.

Although there has been described a preferred embodiment of this novelinvention, many variations and modifications will now be apparent tothose skilled in the art. Therefore, this invention is to be limited,not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. An electromagnetic device including a magnetic frame having a firstand a second section; coil means mounted in magnetic coupling relationto said frame whereby a flow of electric current in said coil meansgenerates magnetic flux in said frame; an assembly including said firstsection; biasing means urging said assembly and said second section awayfrom each other to a released position; said assembly also including apermanent magnet of suflicient holding power to maintain said assemblyand said second section adjacent to each other in a latched positionwhen said coil means is deenergized; a iirst and second energizingcircuit for said coil means; said first circuit when energized causingcurrent fiow in said oil means in a direction generating a rst magneticflux aiding a second magnetic flux of said permanent magnet with theresultant of said first and said second fluxes being of sufiicientstrength to overcome said biasing means and operate said assembly andsaid second section to said latched position; said second circuit whenenergized causing current fiow in said coil means in a directiongenerating a third magnetic flux opposing said second iiux with theresultant of said second and said third fluxes causing said assembly andsaid second section to be released from each other enabling them to beoperated by said biasing means to said released position; said firstsection being generally E-shaped with a base, relatively narrow outerlegs and a relatively wide center leg; said legs extending generally inthe same direction from said base, said magnet positioned at the baseend of said center leg and interposed between said center leg and saidcenter leg and said base; said magnet comprising a plate-like membermagnetized perpendicular to the plane thereof; said legs being generallyperpendicular to said plane, said first section comprising a first stackof generally U-shaped laminations including said base and said outerlegs, and a second stack of generally I-shaped laminations includingsaid center leg.

2. A device as set forth in claim 1 in which said second stack at theend thereof closer to said magnet includes first and second projectionsextending in opposite directions toward said outer legs but terminatingshort thereof.

3. A device as set forth in claim 2 in which said magnet is rectangularand said projections extend beyond the shorter sides of said magnet.

`4. A device as set forth in claim 1 in which said assembly includesretainer means for maintaining said stacks and said magnet in operativepositions; said retainer means including first and second side plates ofrelatively low magnetic permeability with said stacks and said magnetpositioned between said side plates.

S. A device as set forth in claim `4 in which each of References Citedsaid plates are constructed of stainless steel. UNITED STATES PATENTS 6.A device as set forth in claim 1 in which said stacks 2,876,397 3/1959Wasson 335 230 are provided with formations cooperating to form a shal-3 153 178 10/1964 Martin 335 234 low recess wherein said magnet isdisposed.

7. A device as set forth in claim 1 in which said second FOREIGN PATENTSsection includes an armature part having a at surface 245,088 1&0/ 1966Austria. which engages said legs when said second section is in said983,303 2/ 1965 Great Britain.

latched position.

8. A device as set forth in claim 7 in which said arma- 10 G' HARRISPrlmary Exammer ture part comprises a single sheet of material havingrela- U.S. Cl. X.R. tively high magnetic permeability. 317-150; 335-253

